To summarize the current scenario is as follows

[shaownhasan]

The desktop is still very important , so DO NOT forget about it

Mobile is overtaking desktop in quantity and quality (€) of traffic

An online business can NO LONGER afford to have a site that is not mobile some of the key features of band friendly (and I don't mean the former Google label, but in the operational sense of the term)

The available solutions are (with Mobile I also mean the “Dynamic” solution):

Responsive

Responsive + AMP

Desktop + Mobile

Desktop + Mobile + AMP

Desktop + AMP

Personally, I believe that today (so with Google's algorithms in check) for a news site the Responsive + AMP choice (for news only) is the best.

For an ecommerce site I believe that the choice of Desktop + Mobile is still the most rewarding, where I would invest the cost of AMP development in improving the user experience (UX) on mobile, still too much neglected today.The same thing happens in UIs. The back, undo, share and reply functions are often represented with very similar arrows.

Using these symbols close to each other, without a label (text label) increases the user's cognitive load, doubt, and frustration.